(1) Field of the Invention
The invention relates to a marking paint ball and the method for making same.
(2) Prior Art
For military or police practice, or sports or leisure activities (particularly “Paintball”), compressed gas guns and marking paint balls are used.
The term marking paint ball refers, according to the present invention, to a capsule generally having a spherical shape, comprising a shell and a marking paint composition contained in said shell.
In this context, the nature of the constituent material of the shell and the dimensional characteristics thereof (particularly the thickness) must be such that the impact generated by a ball on a target causes the bursting of the shell and the dispersion of the marking paint composition on the target, indicating that said target has been hit.
At the present time, such a ball is produced with a gelatin shell according to a known method conventionally used for the production of medicinal products. This method comprises the formation by means of thermoforming of two hemispheres, which are assembled together, whereas the marking composition is introduced into the cavity defined by the two hemispheres.
However, this ball involves numerous problems associated with the nature of the shell.
Indeed, given that gelatin is of animal origin, the preparation thereof is difficult and it is difficult to obtain a consistent and reproducible composition. Furthermore, the production of gelatin balls must be performed under controlled atmospheric conditions due to the high sensitivity of gelatin to humidity and temperature. This is generally conveyed as follows: from a certain humidity level, gelatin softens, whereas at high temperatures, it tends to dry. Moreover, in the event of freezing, the water contained in gelatin crystallizes, resulting in the gelatin losing some of the mechanical properties thereof.
The production of gelatin balls generally comprises a hemisphere thermoforming step, generally followed by a drying step for a relatively long period, typically between one and a plurality of days.
Furthermore, with respect to the packaging of said balls once produced, the packaging must be hermetic, for example in a sealed (sometimes in a vacuum) wrapper, particularly due to the high sensitivity of gelatin to humidity and temperature conditions.
Moreover, depending on the environment of said balls during the use thereof, the mechanical properties thereof, particularly the burstability thereof following the impact on the target, and the dimensions thereof may vary, rendering same imprecise, or even unusable, such that it becomes difficult to control the life cycle thereof. The term ball having a controlled life cycle refers, according to the present invention, to a ball having a predetermined life cycle from the production thereof to the bio-assimilation thereof, and wherein the mechanical properties are controlled.
Finally, the sensitivity of gelatin to humidity requires the use of non-water-based paint compositions based on solvents such as ethylene-glycol, polyethylene-glycol or polypropylene-glycol. These non-water-based paint compositions are generally in the form of viscous gels and contain solvents which are absolutely not environmentally friendly.
To solve the abovementioned problems associated with the use of gelatin in the production of the ball shell, those skilled in the art have sought another material not involving the drawbacks of gelatin.
In this way, the European patent application EP 0 609 298 discloses a marking paint ball wherein the shell is made of polystyrene with molecular lines oriented along circumferential lines between two poles. These lines are weakened, which is favorable for the bursting of the ball following the impact thereof on a target. The ball is produced by assembling two hemispheres by means of pressurized injection, followed by bonding or sealing. While such a ball may do away with the stability problems usually encountered by balls wherein the shells are made of gelatin, the production thereof remains costly as it makes use of a pressurized injection technique and requires the handling of the hemispheres prior to the assembly thereof.